Unloader valve assembly

ABSTRACT

An unloader valve assembly includes a cylindrical housing defining an annular space, an inner wall thereof including a port that enables fluid communication between the annular space and a location outside the inner wall of the housing. A mandrel having a tubular configuration is positioned inside the housing, the mandrel defining a central bore for receiving fluid and includes a mandrel port enabling fluid communication between the central bore and the annular space. A piston encircling the mandrel is movable along an axis defined by the central bore. A spring is situated between the inner wall of the housing and the mandrel and movable between an extended configuration urging the piston downwardly and a compressed configuration being urged upwardly by the piston.

REFERENCE TO RELATED APPLICATIONS

This application claims the priority and benefit of provisional patent application U.S. Ser. No. 62/508,022 filed May 18, 2017 titled Unloader Valve which is incorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to downhole oil and gas equipment and in particular to that of a valve that enables seal mandrels to enter closed bores which are normally impractical due to the incompressibility of fluid. The aforementioned condition is commonly referred to as being “fluid locked”.

It is common practice to install plugs, packers, barriers, and retainers at various depths within a well bore. These devices are used for a myriad of remedial services for oil and gas wells. Frequently, devices are set in the casing of a wellbore and act as plugs where such devices contain a sliding sleeve that will require shifting to selectively open and shut off a communicative flow path from above to below the plug. As an example, a loosely defined rudimentary system for the purpose of squeezing cement below a plug is illustrated herein in conjunction with the invention to demonstrate its' functionality.

A particular type of plug or barrier is commonly referred to as a “cement retainer.” The cement retainer is deployed with its' sliding sleeve in the closed position and within the casing to a desired depth then locked to the casing via grippers called “slips.” At the same time as the slips are set, an elastomer is expanded against the inside wall of the casing thus shutting off communication from above or below the cement retainer. A subsequent deployment into the casing is required with a mandrel connected by pipe to the surface. Such mandrel is designed to seal within the upper bore of the cement retainer and shift the sleeve to the open position upon contact with the sleeve. With the sleeve in the open position, the seals of the mandrel shut off communication around the outside of the mandrel while the expanded elastomer of the cement retainer shuts off communication around the outside of the cement retainer. Cement pumped through the pipe from the surface, exits through the open sleeve and fills the area of the casing located below the cement retainer. The remedial operation of squeezing cement below the retainer normally takes place within a well that has no pressure, therefore, the top of the pipe at surface can be open to the atmosphere when the mandrel is stabbed into the upper bore of the cement retainer preventing a condition referred to as “fluid lock”. In some circumstances, remedial cement squeezing is advantageous within a well bore that is pressurized. The pipe must be closed at the top to contain the pressure. In addition, check valves that prevent back flow into the pipe are commonly installed near or directly above the mandrel A small volume of fluid is trapped between the check valves and the bore of the cement retainer when the seals of the mandrel contact the upper bore of the cement retainer creating a fluid lock condition. Due to the limited compressibility of fluids, pressure increases while additional penetration is attempted to reach and shift the sleeve within the cement retainer. Unless the pressure can be relieved, the mandrel may be prevented from reaching the sleeve to accomplish shifting of the sleeve to the open position.

Therefore, it would be desirable to have a a valve that enables seal mandrels to enter closed bores of plug elements, such as a cement retainers, and displace trapped fluids so as to overcome the fluid lock problem often encountered in a well boring process.

SUMMARY OF THE INVENTION

The invention disclosed herein advantageously eliminates the fluid lock condition by providing a space for displacement of trapped fluid thus allowing the mandrel to reach and successfully shift a sleeve within a cement retainer. The cement retainer system used as an example herein is not intended to limit the invention to use with such system. Many circumstances exist that can create a fluid lock condition whereby this invention can be employed to alleviate such a condition. The aforementioned features and functions will be fully defined in the detailed description of the disclosure.

Therefore, a general object of this invention is to provide a valve assembly for use in drilling a well bore that eliminates the fluid lock condition by providing a space for displacement of trapped fluid thus allowing the mandrel to reach and successfully shift a sleeve within a cement retainer.

Other objects and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, embodiments of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-section view of an unloader valve according to a preferred embodiment of the present invention.

FIG. 2 is a side cross-section view of the unloader valve installed in a typical arrangement with associated devices to perform cementing through a typical cement retainer and prior to mandrel seal contact with the upper bore of the cement retainer.

FIG. 3 is side cross-section view of the unloader valve and associated devices with the sleeve within the cement retainer fully shifted sleeve by contact with the mandrel.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An unloader valve assembly according to a preferred embodiment of the present invention will now be described with reference to FIGS. 1 to 3 of the accompanying drawings.

Referring to FIG. 1, the unloader valve assembly 10 is comprised of upper adapter 101, housing 116 having a cylindrical configuration (which may also be referred to merely as “cylinder”), lower adapter 123 (which may also be referred to as a bottom adapter), mandrel 104, piston 110, spring guide 108, and spring 103, the connections and combinations of which will be described below in more detail.

Still referring to FIG. 1, upper adapter 101 includes upper thread 100 for securing associated tools and/or pipe. Upper adapter is coupled to an upper end of housing 116 and is operable to receive and engage a check valve assembly as described later. Lower thread 102 of upper adapter 101 secures upper adapter 101 to housing 116 and seal 115 encircles mandrel 104. Housing 116 is secured by thread 113 (i.e. a threaded arrangement) to lower adapter 123 encircling piston 110, spring guide 108, mandrel 104, and spring 103. As described in more detail later, lower adapter 123 may be configured and capable of operably engaging a seal mandrel assembly as will be described more fully below with reference to FIG. 5.

Spring 103 may be a compression spring as will be described later. Spring 103 includes an upper end or portion operably coupled (meaning there may be intermediate structures) to upper adapter 101 and includes a lower end or portion operably coupled to piston 110, spring 103 being positioned between the inner wall of housing 116 and mandrel 104. The spring 103 may be a compression spring and is movable between and extended configuration and operable to urge or force piston 110 downwardly (i.e. away) and a compressed configuration when urged upwardly by movement of piston1 110. Spring 103 is normally biased toward the extended configuration, i.e. away from being compressed. The side wall (which will also be referred to as inner wall) of the housing 116 defines port 105, port 105 being operable for communication of fluid between the annular space 121 and a location outside of the annular space 121. Lower adapter 123 includes thread 124 (i.e. a threaded arrangement) for securing associated tools. Seal 122 seals against the bore of housing 116. Spring 103 is normally biased toward an extended configuration that covers port 105 but is movable to a compressed configuration in housing 116 that leaves port 105 open. Port 105 is in fluid communication with the annular space 121 described later in more detail.

Piston 110 encircles a lower portion of mandrel 104. Piston 110 includes an inner seal 119 that encircles piston 110 and seals against the outer diameter of mandrel 104 and outer seal 109 of piston 110 seals against the bore of housing 116. The lower most section of piston 110 includes ports 111 that define a path of communication between central bore 114 and annular space 121. The lower adapter 123 includes upper end 112 and lowerly adjacent ports 111.

An upper end of piston 110 has an upward facing shoulder 118. Spring guide 108 abuts upward facing shoulder 118 of piston 110 and the bottom of spring 103, i.e. is intermediate the two structures. Mandrel 104 is confined within the lower bore of upper adapter 101 extending to the upper bore of lower adapter 123. Mandrel 104 may also have a tubular configuration defining the central bore 114 operable to transfer a flow of fluids.

It is understood that central bore 114 defines an imaginary linear axis about which many components encircle, such as piston 110 encircles mandrel 104 and is movable (e.g. slidable) therealong and along the imaginary linear axis. The mandrel 104 includes mandrel port 120 which provides a path of communication between central bore 114 and annular space 121. The unloader valve 10 includes spring 103 that encircles mandrel 104 and is confined between the lowermost shoulder of upper adapter 101 and upward facing shoulder of spring guide 108, spring 103 selectively urging piston 110 downward to abut the upper most shoulder of lower adapter 123 as will be described further below.

Referring to FIG. 2, unloader valve assembly 10 is attached by its upper adapter thread 100 to a representative flapper style check valve 300 and by its lower adapter thread 124 to a representative seal mandrel assembly 500. Seal mandrel assembly 500 is shown suspended and positioned partially within the upper bore 605 of a representative and rudimentary cement retainer assembly 600. Check valve assembly 300 is secured by thread 201 to pipe 200 extending to the surface. Cement retainer assembly 600 is shown anchored to the wall 402 of casing 400 by its slips 601 and 607 and seal element 606 seals against the bore 402 of casing 400 shutting off communication around cement retainer assembly 600. Sliding sleeve 603 within cement retainer assembly 600 is shown in the closed position with seals 604 and 608 straddling port 609 in the lower sidewall of cement retainer assembly 600 shutting off communication between the upper bore 401 of casing 400 and lower bore 403. Collet fingers atop the sliding sleeve 603 maintain the closed position of sliding sleeve 603. The flapper 301 of check valve assembly 300 is shown in the open position as fluid is pumped in a path of circulation through central bore 114 and around the end of seal mandrel assembly 500 and upward into the bore 401 of casing 400.

Referring to FIG. 3, flapper 301 of check valve assembly 300 is shown urged by a torsion spring (not shown) to a closed position as a result of fluid circulation ceasing prior to seals 501 of seal mandrel assembly 500 entering upper bore 605 of cement retainer assembly 600. Upon initial contact between seals 501 of seal mandrel assembly 500 and upper bore 605 of cement retainer assembly 600, fluid is trapped between flapper 301 of check valve assembly 300 and the closed sliding sleeve 603 of cement retainer assembly 600 (FIG. 2). Continued lowering of pipe 200 urges seal mandrel assembly 500 further into the upper bore 605 of cement retainer assembly 600 which displaces the fluid within bore 605 which causes a pressure increase within central bore 114. The pressure increase acts against the bottom of piston 110 through port 120 of mandrel 104 so as to urge piston 110 upward compressing spring 103. Piston 110 moves upward in unison with the displaced fluid as seal mandrel assembly 500 continues to penetrate the bore 605 of cement retainer assembly 600. Fluid above piston 110 is permitted to exhaust through port 105 in the sidewall of housing 116 as piston 110 moves upward. The annular space 121 created by the upward movement of piston 110 is sufficient in volume to contain the entire volume of fluid displaced by the penetration of seal mandrel assembly 500 into the upper bore 605 of cement retainer assembly 600.

Referring to FIG. 1, upward movement of piston 110 is abated by contact of upward facing shoulder 107 of spring guide 108 when contacting downward facing shoulder 117 of mandrel 104 thus preventing possible communication between central bore 114 and port 105 of housing 116 however. Whenever piston 110 is displaced upward prior to contact between downward facing shoulder 117 and upward facing shoulder 107, annular space 121 is greater in volume than the displaced volume of fluid created by the penetration of seal mandrel assembly 500 into the bore 605 of cement retainer assembly 600.

Referring to FIG. 3, the upward moving piston 110 of unloader valve assembly 10 advantageously allows the seal mandrel assembly 500 to fully penetrate bore 605 of cement retainer assembly 600 and contact sliding sleeve 603 of cement retainer assembly 600 shifting the sliding sleeve 603, thus opening a path of communication through ports 609 of cement retainer assembly 600.

It is understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and allowable functional equivalents thereof. 

1. An unloader valve assembly for engaging, via a seal mandrel assembly, a cement retainer assembly that is deployed inside a casing of a well bore and that is attached to the casing with slips and having a sliding sleeve initially in a closed configuration not allowing fluid to flow into proximity of the cement retainer assembly from a check valve assembly having a flapper at an open configuration, the sliding sleeve being slidably movable to an open configuration upon downward urging of the seal mandrel assembly into engagement with the cement retainer allowing fluid to flow from the check valve assembly into the casing, said unloader valve assembly, comprising: a housing that includes an inner wall having a cylindrical configuration defining an annular space; wherein said inner wall of said housing includes a port that enables fluid flow between said annular space and a location outside said inner wall of said housing; an upper adapter coupled to an upper end of said housing and operable to engage the check valve assembly; a lower adapter coupled to a lower end of said housing and operable to engage the seal mandrel assembly; a mandrel positioned inside said interior space of said housing and inwardly displaced from said inner wall of said housing, said mandrel having a tubular configuration defining a central bore for receiving a flow of fluid; wherein said mandrel includes a mandrel port operable for fluid communication between said central bore and said annular space; a piston encircling said mandrel that is movable along an axis defined by said central bore when urged to move; a spring having an upper end operably coupled to said upper adapter and a lower end operably coupled to said piston, said spring being situated between said inner wall of said housing and said mandrel and movable between an extended configuration urging said piston downwardly and a compressed configuration being urged upwardly by said piston.
 2. The unloader valve assembly as in claim 1, wherein said spring is naturally biased toward said extended configuration so as to urge said piston downwardly to bear against said lower adapter.
 3. The unloader valve assembly as in claim 1, wherein a volume of said annular space is increased when said piston is urged upwardly in said annular space and said spring is moved toward said compressed configuration.
 4. The unloader valve assembly as in claim 3, wherein said annular space has a volume sufficient to contain an entire volume of fluid displaced by penetration of the seal mandrel assembly into the cement retainer assembly.
 5. The unloader valve assembly as in claim 2, wherein a pressure increase in said central bore is communicated through said mandrel port and bears against a bottom of said piston so as to urge said piston upwardly to compress said spring toward said compressed configuration.
 6. The unloader valve assembly as in claim 5, wherein fluid in said central bore is allowed to flow from said central bore through said port in said inner wall of said housing to said location outside said housing as said piston is urged upwardly.
 7. The unloader valve assembly as in claim 6, wherein said piston moves upwardly in unison with fluid being displaced by penetration of the seal mandrel assembly into the cement retainer assembly.
 8. The unloader valve assembly as in claim 1, wherein: said upper adapter is coupled to said housing in a threaded engagement; said lower adapter is coupled to said housing in a threaded engagement.
 9. An unloader valve assembly, comprising: a housing that includes an inner wall having a cylindrical configuration defining an annular space; wherein said inner wall of said housing includes a port that enables fluid flow between said annular space and a location outside said inner wall of said housing; an upper adapter coupled to an upper end of said housing and operable to engage a check valve assembly; a lower adapter coupled to a lower end of said housing operable to engage a seal mandrel assembly; a mandrel positioned inside said interior space of said housing and inwardly displaced from said inner wall of said housing, said mandrel having a tubular configuration defining a central bore for receiving a flow of fluid; wherein said mandrel includes a mandrel port operable for fluid communication between said central bore and said annular space; a piston encircling said mandrel that is movable along an axis defined by said central bore; and a spring having an upper end operably coupled to said upper adapter and a lower end operably coupled to said piston, said spring being situated between said inner wall of said housing and said mandrel and movable between an extended configuration urging said piston downwardly and a compressed configuration being urged upwardly by said piston.
 10. The unloader valve assembly as in claim 9, wherein said spring is naturally biased toward said extended configuration so as to urge said piston downwardly such that said piston bears against said lower adapter.
 11. The unloader valve assembly as in claim 9, wherein a volume of said annular space is increased when said piston is urged upwardly in said annular space and said spring is moved toward said compressed configuration.
 12. The unloader valve assembly as in claim 9, wherein a pressure increase in said central bore is communicated through said mandrel port and bears against a bottom of said piston so as to urge said piston upwardly so as to move said spring toward said compressed configuration.
 13. The unloader valve assembly as in claim 5, wherein fluid in said central bore is allowed to flow from said central bore through said port in said inner wall of said housing to said location outside said housing as said piston is urged upwardly.
 14. The unloader valve assembly as in claim 9, wherein: said upper adapter is coupled to said housing in a threaded engagement; said lower adapter is coupled to said housing in a threaded engagement.
 15. An unloader valve assembly for placement in a casing of a well bore, comprising: a seal mandrel assembly situated in the casing; a check valve assembly having a flapper member positioned in the casing for insertion of a fluid into the casing; a cement retainer assembly positioned inside the casing lowerly adjacent said seal mandrel assembly and coupled to a wall thereof with slips and having a sliding sleeve initially in a closed configuration not allowing fluid to flow into proximity of the cement retainer from said check valve when said flapper is at an open configuration, said sliding sleeve being slidably movable to an open configuration upon downward urging of said seal mandrel assembly into engagement with said cement retainer assembly allowing fluid to flow from the check valve assembly into the casing; a housing situated within the casing between said check valve assembly and said seal mandrel assembly and that includes an inner wall having a cylindrical configuration defining an annular space; wherein said inner wall of said housing includes a port that enables fluid flow between said annular space and a location outside said inner wall of said housing; an upper adapter coupled to an upper end of said housing and operable to engage said check valve assembly; a lower adapter coupled to a lower end of said housing and operable to engage said seal mandrel assembly; a mandrel positioned inside said interior space of said housing and inwardly displaced from said inner wall of said housing, said mandrel having a tubular configuration defining a central bore for receiving a flow of fluid; wherein said mandrel includes a mandrel port operable for fluid communication between said central bore and said annular space; a piston encircling said mandrel that is movable along an axis defined by said central bore when urged to move; a spring having an upper end operably coupled to said upper adapter and a lower end operably coupled to said piston, said spring being situated between said inner wall of said housing and said mandrel and movable between an extended configuration urging said piston downwardly and a compressed configuration being urged upwardly by said piston.
 16. The unloader valve assembly as in claim 15, wherein a volume of said annular space is increased when said piston is urged upwardly in said annular space and said spring is moved toward said compressed configuration.
 17. The unloader valve assembly as in claim 16, wherein said annular space has a volume sufficient to contain an entire volume of fluid displaced by penetration of said seal mandrel assembly into an upper bore of said cement retainer assembly so as to displace fluid therefrom.
 18. The unloader valve assembly as in claim 17, wherein said fluid displacement causes a pressure increase in said central bore that is communicated through said mandrel port and bears against a bottom of said piston so as to urge said piston upwardly to compress said spring toward said compressed configuration.
 19. The unloader valve assembly as in claim 18, wherein said piston moves upwardly in unison with fluid being displaced by penetration of the seal mandrel assembly into the cement retainer assembly.
 20. The unloader valve assembly as in claim 15, wherein fluid in said central bore is allowed to flow from said central bore through said port in said inner wall of said housing to said location outside said housing as said piston is urged upwardly. 